Polymeric sealants have a wide variety of applications, and are widely used in manufacturing industries such as the automotive industry and the building trades industry. In the automotive industry, sealants are widely used to seal fixed glass panels to vehicle body panels. Polymer sealants are generally pigmented or unpigmented synthetic elastomeric polymers that form pourable or easily-extrudable mastics in the uncured state. When cured, the sealants are transformed into elastomeric materials that have viscoelastic properties, and can react to the relative motion of the structural elements with which the sealant is brought into contact to form a seal. The cured sealants thus form a tight barrier against moisture, gases, and chemicals.
Sealant compositions are often based on polysiloxane polymers as well as others that include polyurethane or polyacrylate polymers. Sealant compositions can be of the one-part or two-part variety, which cure by a variety of chemical mechanisms. One-part sealant compositions generally contain an end-capped base polymer together with a reactive cross-linking agent and, usually, a curing catalyst that promotes the cross-linking reaction either when heated or exposed to atmospheric moisture. Upon application under normal conditions of temperature and moisture, one-part sealants react to form tough, pliable elastomeric seals.
Two-part sealant compositions, on the other hand, comprise two reactive components that are separately packaged and mixed just prior to or at the time of application and react upon mixing to form the semi-rigid sealant bead. Two-part sealant compositions, are less convenient to use since it is necessary to accurately premeasure and mix the components prior to use or accurately meter the component during application to insure correct proportions. For this reason, one-part sealants have found wider acceptance in the market. A number of such one-part moisture-curable sealant compositions are known.
In modern automotive design construction, the windshield is an integral part of the structural integrity of the vehicle. Thus, it is critical that the windshield sealant securely bond the windshield to the vehicle body panels. One-component moisture cure sealant possess many advantages, but fall far short of the requirements with respect to adhesion to a variety of surfaces. It is therefore often necessary to coat the glass with a primer prior to adhering and sealing it to the vehicle body panel. It would thus be desirable to provide a one-part sealant that exhibited good adhesion to a variety of surfaces, particularly when one of the surfaces is glass either with or without a glass primer.